The chemical vapor deposition of metal and metal-containing films on dielectric substrates is of great interest in many areas of semiconductor fabrication, such as deposition of metal wiring, electrodes, and diffusion barriers. In particular, thin films of ruthenium, Ru, and ruthenium oxide, RuO2, are useful in integrated circuit devices and in fabrication of integrated circuits. Ruthenium and ruthenium oxide are generally useful as electrical contact materials. They have good electrical conductivity and show good environmental stability. They are useful for contact metallizations, diffusion barriers, and gate metallizations. Ruthenium oxide electrodes have also shown utility as working electrodes in non-aqueous solvents. Ruthenium and ruthenium oxide are useful as capacitor electrodes that remain electrically conductive even after exposure to oxidizing conditions. A thin film of ruthenium metal deposited on a wafer substrate is useful as a seed layer on which copper is deposited by electrochemical or electroless chemical plating techniques.
Deposition of copper wiring in integrated circuits involves a number of processes. Typically, a trench or hole is etched into dielectric material located on a substrate wafer. The hole or trench then is typically lined with one or several adhesion and diffusion-barrier layers; for example, with tantalum nitride, TaN. The hole or trench then is lined with a thin layer of copper, Cu, that acts as a seed layer for electroplated copper. Thereafter, the hole or trench is filled with copper, typically by an electroplating process. In the past, adhesion layers, barrier layers and copper seed layers lining holes and trenches were deposited using conventional physical vapor deposition techniques. As the design density of integrated circuits increases, resulting in smaller dimensions of holes and trenches, it is generally more difficult to use physical vapor deposition to line holes and trenches with uniform and conformal thin films of integrated circuit material.
As the design density of integrated circuits increases, resulting in smaller design features and dimensions, deposition of ruthenium and ruthenium oxide thin films, as well as thin films of other materials, by physical vapor deposition techniques is often unsatisfactory for obtaining good quality, continuous, and conformal thin films. As a result, deposition of ruthenium metal, ruthenium oxide, and other metal compounds by chemical vapor deposition (CVD) and atomic layer deposition (ALD) is important for achieving good circuit quality and acceptable manufacturing yields.
Thus, the chemical vapor deposition of metal films on integrated circuit substrates is of great interest in many areas of semiconductor fabrication. Chemical vapor deposition of metal directly onto a dielectric material, such as silicon oxide, SiO2, or onto standard adhesion layer material, such as tantalum nitride, TaN, is often accompanied by delayed and discontinuous growth, surface roughness and poor adhesion. These problems are especially acute in processes for depositing ruthenium on silicon oxide (SiO2) without a seed layer. Many other metal CVD processes, for example, MOCVD of copper, suffer these problems also.
Techniques are known for improving the nucleation and adhesion of chemical vapor deposition of metallic material onto integrated circuit substrates. For example, U.S. Pat. No. 6,605,549, issued Aug. 12, 2003 to Leu et al., discloses plasma treatment with O2, N2O or H2 plasma of a dielectric surface prior to CVD or ALD deposition of a barrier film, such as TaN, Ti, TiN, and WTa. U.S. Pat. No. 6,638,859, issued Oct. 28, 2003 to Sneh et al., discloses pretreating a surface using a radical species (e.g., plasma made from O2, H2, OH, NH2, Cl or F) prior to ALD metal deposition to make the substrate surface reactive so that the ALD process can start continuously without nucleation or incubation.
Pretreating a substrate surface with iodine has been reported to increase the growth rate of copper deposited by a MOCVD technique using Cu(hfac)TMVS precursor. U.S. Pat. No. 6,413,864 issued Jul. 2, 2002 to Pyo et al., discloses forming a copper seed layer on a nitride barrier layer surface (e.g., TiN, TaN, WN), then forming a chemical enhancement layer (CE layer) with an iodine-containing liquid compound prior to forming a first copper layer by MOCVD, and then electroplating a second copper layer onto the first copper layer. U.S. Pat. No. 6,468,907 issued Oct. 22, 2002 to Pyo et al., discloses forming a CE layer on a nitride barrier layer surface (e.g., TiN, TaN, WN) with an iodine-containing liquid or gas (or F, Cl, Br, I or At gas), and then removing part of the CE layer prior to filling a damascene pattern with a copper (or Al or W) layer using MOCVD. U.S. Pat. No. 6,593,236 issued Jul. 15, 2003 to Pyo et al., discloses forming a CE layer on a copper seed layer with an iodine-containing liquid or gas (or F, Cl, Br, I or At gas), then removing part of the CE layer by plasma while partially filling a damascene pattern with a copper layer using MOCVD, then electroplating copper. A CE layer of Pyo et al. accelerates or increases the deposition rate of copper onto the CE layer compared to portions of the substrate having no CE layer.
Kwon et al. describe I2 plasma treatment that increases the film growth rate of copper by MOCVD on a SiO2 or TiN surface. “Enhancement of Iodine Adsorption Using I2 Plasma for Seedless Catalyst-Enhanced CVD of Copper”, Electrochemical and Solid-State Letters, 6 (8) C109–C111 (2003). Other reports in the literature describe the use of surfactants, such as Sb, Pb, CO, H2O, S, and I (iodine), to suppress agglomeration, promote layer-by-layer growth and increase the deposition rate in metal epitaxy. Mechanisms involved are often unclear, but the effects are attributed to a change in surface-diffusion activation energy, leading to a decrease in adatom mobility of the depositing metal in the presence of the surfactant. Adsorption of iodine and some other surfactants onto less-reactive surfaces, such as TiN, TaN and other metal nitrides used for diffusion barriers, and particularly onto nonmetal dielectric surfaces (e.g., SiO2), however, has not been demonstrated to achieve good thin film morphology of ruthenium and of some other metals.
The chemical vapor deposition of metal films on dielectric substrates is often difficult due to the inability of the metal to nucleate on dielectric surface. This leads to long process times, poor adhesion and surface roughness. The deposition of a metal thin film, particularly of ruthenium, Ru, or other Ru-containing layer by chemical vapor deposition (such as MOCVD and ALD) without a metal seed layer often results in poor morphology of the thin film.